There are T-joint fittings adapted to be attached to a length of pipe at a selected point thereof, and which encloses a piston which is axially displaceable in a passage by the firing of cartridge. The piston will cut a hole in the pipe and the piston is provided with a transverse passage, which in a final position will permit the transfer of fluid from the pipe to a second passage in the fitting, and further on to a branch pipe communicating with said second passage.
A T-joint fitting of this type is i.a. shown in U.S. Pat. No. 3,983,897 to S R V Gebelius of Stockholm, Sweden.
With earlier types of fittings the powder charges used to perform the work of cutting the hole in the pipe and of compressing the chip, so obtained, provided much higher thrust than necessary.
The present development ensures a more adequate control of the hole cutting process, which means that it will be easier to calculate the energy necessary, so excess input of powder can be avoided.